Screw tapping machine



May Z0, 1941. J. A. EDEN ETAL SCREW TAPPING MACHINE.

Filed July 5, 1940 INVENTORS JAMESA-EDE'M BY HAERYIDHILL/Ps @bv/I WQ/LATTORNEY' o H MWZW I 2 v qMowm/NWKJM al Mu MMNMMMMD l i627 MM IMZQSMI O6 Tm w WMMEMM 07 I7 .w M2ZM44M F I 0 2 5 ,36 H 2 WZMMFDG C |1 76 T M MZEMMMW 6 al D.. 2 WQMMMM ma. 424 MnmH/IV/l/VQ RF cl3 IIIlll T0 m O May2o,1941. A EDEN ETAL 2,242,293

SCREW TAPPING MACHINE Filed July 5, 1940 6 Sheets-Sheet 2 INV ENTORS M w Q JIMES IDEDE/v. BY MQ- APR'Y H/LL/Ps.

ATTORNEY May20,1941. M. EDEN Em 2,242,215:

SCREW TAPPING MACHINE Filed July 5' 1940 6 Sheets-sheet 3 m V m5 M ENQ/,KW WEL T DL T .FM AV, MA @W Y@ .B

May 20, 1941- J..A. EDEN ETAL. 2,242,293

l scREw TAPPING MACHINE l Filed July 5, 1940 6 Sheets-Sheet 4 INVENTORS` J2 MEJ A. EDE/V.

BY HA ERrPH/LL/Ps.

ArTozr/EY May2o,1941. J, EDEN ETAL 2,242,293

SCREW TAPPING MACHINE Filed July 5, 1940 sfsheets-sheet 5 J. A. EDEN ETAL SCREW TAPPING MACHINE May 20, 1941.

6 sheets-sheet' rs44 Filed July 5, 1940 i///////'///////////////A l .z REVERSE BUTTON AHEAD r. BUTTON fea 11\IVENTOR5 JA MES AEDE/v.

ATTORNEY HAREYPH/L/Rs'.

Patented May 20, 1941 SCREW TAlPIN G MACINE James' A. Eden and Harry Phillips, Springfield,

Mass., asslgnors to Baush Machine'Tool Company, Springeld, Mass., a corporation of Massachusetts Application lJuly 5, 1940, serial No. 344,102

(ci. 1o-129) 20 Claims.

Our invention relates to a machine for tapping screw threads in bores or openings, and more par.

ticularly to a tapping machine of the above type inwhich the threads may be cut or tapped withl great accuracy and to a predetermined depth or number of threads. v

In certain mechanisms as, for example, in aircraft and aircraft engines, bores or openings must be tapped with suficient accuracy so that when a threaded shank is screwed into the openings it will have no play, or substantially no play, inthe threads of the opening. It is also necessary that the depth of the threads be accurately controlled, the tolerance of about one and one-half turns overl the threads required for the nut or screw being generally the maximum permitted.

To attain this accuracy it has generally been necessary to tap the bores or openings by hand, and great skill has been required to set and turn x the tap in the b ore or opening without exerting such pressure as would enlarge the cut in any way and thus give too loose a t.

y In our present invention we provide a machine whereby bores or openings may be tappedwith an accuracy excelling that obtained by the best -v skilled hand work and in which the depth of the tapping may be accurately controlled.

Our invention also provides mechanism whsere.- by the tap may be quickly and easily placed in position on a Work piece and in which taps of.

different pitch and size maybe quickly and easily mounted in the mechanism. The mechanism also rotations so as to cut a predetermined number of threads, or to tap the bore or opening to \a predetermined depth.

'This mechanism comprises a counting deviceor di'erential mechanism, one part of which may be rotated independently to the position indicated provides means guarding against any possible in- Jury to the work piece or to the mechanism, in case of failure of 'the operator to position the tap, or due to any other error in setting they mechanism in operation.

In our invention a tapof selected size and pitch is carried ina freely floating head which may be easily moved to position to place the tap immediately above a bore to betapped. The tap is then rotated and fed into the bore at a lrate lcorresponding to the pitch of the tap.L

DuringA the rotation and feed of the tap into the bore, the head supporting the tap is freely floating. This permits a play at the upper end of the spindle holding the tap, and of the tap itself, so that the tap is free to follow the threads being cut rather than being forced into'a rigid 'position which might enlarge a thread, or certainof the threads, by the travel of the tap. A control mechanism is also provided, preferably in the head,r which may be'set to give the tap-rotating spindle a predetermined number of on anvindicating dial and set. As the spindle rotates, and when it reaches a position corresponding to that set, a reversing switch is operated to reverse the rotation of the spindle and tap to withdraw them from the threads cut in the bore or opening.

To prevent breakage or injury to the tap orto the work piece or to the mechanism, the tap-holding mechanism is so mounted that in the event that it is not properly set in the opening or bore and cannot, therefore, be fed into it, the feeding mechanism is displaced under a spring pressure andthe tap -is not forced by the lead screw or feeding. mechanism. l

Anemergency reversing switch is also provided in case it is desirable or necessary to reverse the tap b efore it has proceeded to a depth set by the counting mechanism.

The various features of the invention are illustrated by way of example in the accompanying drawings in which Fig. 1 is a side elevation of a lead screw tapping machine embodying a preferred form of the invention.

Fig. 2 is a chart illustrating a relationship between a thread and the travel of the tap and an example of the dial setting. L

Fig. 3 isan end view of the counting mechanism. A Fig. 4 is a vertical elevation partly in section1 nism in Fig. 4.

Fig. 6 is a vertical section taken on line 6-8 of Fig. 4.

Fig. '7. is a vertical section through the head of the machinetaken on a plane parallel tothat of Fig. 4.

Fig. 8'is a section taken on line 8-8 of Fig. Fig. 9 is a side view of a spindle mounting quill lof the head.

Figs.- 10 and 11 are horizontal sections taken on the unes .ioin and n n. or Fig. '1, respecmounted on a base having an upright part 2| provided at one side with guides 22 for a verti'- cally movable work table 23 on which work pieces to be tapped may be placed and secured. The

work table 23 may be raised and lowered by any suitable or standard mechanism actuated bycrank 24.

As shown more particularly in Figs. 4 and' 6, a hollow supporting cylinder or standard 26 is mounted on the upper end of the upright 2| by means of a flange 26 and bolts-21 and is provided at its upper and lower ends with bearings 28 and 29 respectively, which may be of any suitable type, preferably thrust ball bearings as shown in Fig. 4. A vertical shaft 88 is rotatably supported in the bearings 28 and 29 and carries a carriage 3| above the upper end or edge of the standard 25. The carriage 3i is. therefore, freely rotatable on the vertical axis of the shaft 38.

Slldably mounted in the carriage 3| is a horizontal hollow arm 32 extending through the carriage and carrying a spindle supporting head 33. The arm 32 is slidably mounted in the carriage 3| so that its radial distance from the axis of the shaft 39 may be adjusted or varied, and it swings with the carriage throughout any desired angle or throughout a full revolution. The head 33 may, therefore, be brought to any position within the sweep of the arm 32 by merely sliding it to the desired radial and angular position.

The arm 32 is mounted so as to be firmly held in the carriage and slidable with a minimum of friction by means of two sets of rollers connected on a base plate 34 of the arm 32 on opposite sides of the shaft 30. Each set comprises a pair of lower rollers 35 and 36 supporting the arm near its side edges, and a pair of upper rollers 31 and 38 bearing against bevel side edges 39 and 40 of the base plate 34.

The rollers 35 and 36 are supported on a horizontal shaft 4| mounted at its ends in vertical walls 42 and 43 and freely rotatable on the shaft 4| by means of ball bearings 44 and 45 which are spaced at suitable intervals by means of a spacing sleeve 46. The bearings 44 and 45, and the rollers 35 and 36, are accurately heldin fixed position on the shaft 4| between the sleeve 46 and inward extensions 41 and 48 on the Walls 42 and 43.

The walls 42 and 43 extend upwardly and outwardly to join with the outer wall of the carriage 3|, and in the outwardly inclined part are mounted anti-frlctionalball bearings 49 and 50 for the rollers 31 and 38. n

The inner hubs or raceways of the roller bearings 49 and 50 are mounted on supporting axles 5| and 52 mounted in spaced branches 53 and 54,

\ and 56, respectively, of the walls 42 and 43.

The axles 5| and 52 are secured in place by means of bolts 51 and 58having their heads inset into their respective axles and having ends threaded into the walls 54 and 56 respectively.

The outer'wall of the carriage is provided with suitable openings 59 and 60 to give access to the heads of the screws 51 and 58 so that they may be loosened and tightened to hold the axles in any desired axial position.

'Ihe part of the axle carrying the ball bearing raceways 49 and 50 is mounted eccentrically of the axles so by rotating the axles the rollers may be tightened against the inclined surfaces 39 and 40 so as to take up any play that may be caused by wearing of the plate 34 or of the rollers.

Through the above mounting, the arm 32 is slidable in the carriage with a minimum friction as well as being rotatable freely about the axis of the shaft 30.

At the opposite end of the arm 32, from that supporting the head 33, there is mounted a reversible brake motor 6| for driving the tap and provided with a pulley or set of pulleys 62 of graded or diierent diameters. The pulley 62 is connected through a belt 63 to drive a correspending1 pulley or group of pulleys 64 mounted on the free end of a shaft 65 extending lengthwise through the arm 32 and mounted in suitable bearings 66 and 61, Figs. 4 and` 7, at opposite ends of the arm 32. A housing 68 is provided on fthe end of the arm 32 for the pulleys 62 and 64 and has a hinged cover 69 which may be raised to permit the bellt 63 to be shifted tocontrol the speed of the shaft 65. To change the speed of the shaft 65 the motor 6| may be lowered to release thetension of the belt 63. The belt may then be shiftedand the motor lifted to tension the belt. At its opposite end the shaft 65 extends through the bearing V61 and into the head 33. On the projecting end of the shaft 65 is mounted a bevel gear 18 which meshes with a bevel gear 1| having a hollow shaft 12 extending downwardly to and through a lower antifriction or ball-bearing 13. The bearing 13 supports the shaft 12 and gear 1| and is in turn mounted in 'the upper end of a hollow boss 14 extending upwardly from the bottom of the head.

The shaft 12 is extended above the gear 1| by an extension 15 which is journalled in a bearing 16 mounted in a bracket 11 extending horlzontally above the gear 1| and then vertically in a wall 18. The motor 6| acting through the pulleys 62 and 64, belt 63, shaft 65 and gear 18 serves to drive the gear 1| and the vertical hollow. shaft 12, which in turn drives the tap. For this purpose the lower end of the shaft 12 is bored to receive the upper part of a shaft 19 which is slidably splined in the lower part 89 of the shaft l2. 'Ihe gear 1| thus rotates the shaft 19 which is, however, free to move or slide upwardly and downwardly during rotation.

The shaft 19 extends downwardlybelowthelower end of the shaft 12 and immediately, or shortly below, the end of the shaft 12 is mounted in the inner. raceway 8| of a roller bearing 82, the outer raceway of which is formed in a vertical sleeve or quill 83 thwt is moved upwardly and downwardly in la, hollow depending sleeve or boss 84.

A number of teeth 85 are provided at one side of the quill 83 which mesh with a pinion 86 in the boss 84, which in turn is pinned to the link 81 of crank 88, Figs. 4 and 5.

It will be apparent that by rotatingthe crank 88 and the pinion 86, the quill 83 may be raised and lowered. For example, it may be lowered from the position shown in Fig. '7 by rotating the pinion 86 in a clockwise direction. The upper movement of the quill is limited by a ring or flange 89 at its lower end which may abut the lower end of the boss 84 when the quill 83 is raised to its upper limit. The quill may be kept from turning by longitudinal keyways 90, matching and slidably keyed to keyways 9| in the depending 84, or by ing means.

,/t 2,242,293 anyther suitable retainv The shaft is is rotatable within the quin sa rbut'is held in fixed longitudinal position relative thereto by means of a pin 92 extending through the shaft and through the inner raceway 8| of the bearing 82.' 'I'his bearing is in turn fixed in position relative to the quill 83 between a lower bearing plate 93 supported on a shoulder 94 in the quill, and an upper plate 95 xed on'the upper face of the bearing 82 by means of a ring 96 threaded into the upper end ofthe quill.

It will be apparent Ithat the bearing is thus xed in position on the quill. As the quill is raised and lowered, vthe shaft i9 moves withnit sliding upwardly and downwardly in the lower end of the hollow shaft 12.

Below the bearing 8| the shaft 19 extends downwardly into a closely tting cylindrical recess 91 of a lead screw spindle 98. The lead screw spindle 98 is splined to the shaft 19 by a spline 99 whereby it rotates with, or is rotated by, the shaft 79 but is slidable vertically thereon. The outer surface of the lead screw spindle -98 is .provided with screw threads inv theupper part of the spindle corresponding to rthe pitch of the tap with which the spindle is to be used. These screw threads mesh or thread with internal screw threads of a sleeve i0! fixed in the lower end of thev quill 83 by means of a nut|02 which is threaded into the lower end of the quill 83 and acts as a lower stop -for the lower end of the.

sleeve |0l. The sleeve |0| is slidable inlrthe quill 83 and is kept from rotation by a, suitable slidable spline |03. The sleeve or collar |0| is, however, resiliently held downwardly onto the nut |02 by means of a spring |04 confined between a shoulder |05 on the collar and the bottom of a thrust 'ball bearing |06, the upper part of which 'is secured at the upper end of the lead screw spindle 98? Through this arrangement, when the shaft 'I9 and the lead screw spindle 98 are rotated in such a direction as to feed the spindle 98 downwardly, they compress the springl |04 and hold the collar |0| the more tightly or firmly against ,the

nut |02. However, if the spindle 98 should rest upon a at surface instead of being tted to a being cut, and to that extent provide a :play between the tapped opening and the screw which it is to t."'1he floating support forthe tap spindle, therefore, enables this defect of machine tapped openings to be overcome and enables a .tapped opening to be cut to a ilt conforming accurately to the tap,

For each tap a separate lead spindle andco1-l lar are provided so that the advance of the spindle is always in accordance with the pitch of the tap. The lead spindle and collar assembly may be removed and replaced as a unit by unscrew- `ving the nut |02 whereupon the collar |0| may' be slipped out together with the spring |04, the ball bearing |06, and the spindle 98'and placed in a proper drawer in the table 23. Accidental loosening while removing the nut |02 may be prey vented by a locking member |08.

bore or opening and thus be unable to move downwardly, the threading of the spindle into the collar |0| would thereupon merely lift the collar |0| compressing the spring |04 and thus prevent breakage of any part of the mechanism, or injury to the work piece.

Normally, however, when a tap |01 is mounted inthe lower end of the spindle 90, Figs. 4 and 5, and is positioned to enter an opening or bore to be tapped, th'e rotation of the shaft I9 causes the spindle 98 to be rotated and to be fed downwardly to correspond to the pitch of the tap through the screw threads |00 on the spindle rotating in the screw threads on the inner surface of the `collar |0I. In this manner the tap is set in proper vertical position to enter the bore and is rotated and fed downwardly to correspond to the pitch of the tap but without exerting a greater pressure downwardly. than the force ofthe spring |04 and with the upward end of the tap and of its feed spindle, and the driving shaft in a floating condition so that the upper part of the tap may vibrate as it is rotated.

The vibration is very slight, but if the upper end of the tap were held rigidly, its vibration would take effect or react at the thread cutting edges and tend to enlarge or lgouge the threads ber of rotations given to it.

In tapping a `bore or opening, the quill 83 is lowered and with it the spindle 98 until the g' number of rotations from the start of the tapmay be counted and a mechanism set to stop and reverse the spindle after a predetermined number of rotations.l This counting and control device may be of any suitable construction. That shown in Figs. 10 to 15 inclusive is, however, preferred.

In this arrangement, a pinion |09, Fig. 7, is

.mounted on the end of `the .shaft projecting into the head 33 as, for example, by being mounted onto an extended hub of the gear 10. The gear or pinion |09 meshes with and drivesva gear ||0 mounted on and rotating with a shaft extending through a bearing ||2 in the vertical bracket wall 1.8. The shaft I has a recess in the end and projecting through the vertical extension 18, and in this recess is received and keyed a shaft H3 of the counting and reversing mechanism H4. The shaft 3 is thus rotated with the rotation of the spindle 98 and in a direct proportion or relation therewith to drive the counting and reversing mechanism.

The shaft ||3 extends longitudinally within the casing of control 'mechanism H4, and about midway thereof there is xedly mounted a wide pinion ||5 which meshes at all times with a pinion H6 fixed on a shaft I |1, one end of which is journalled in theend wall |8 of the mechanism, and the other end of which is reduced and received and journalled in a recess I I8' of an aligned shaft ||9, the other end of which is journalled in the opposite end |20 of the reversing mechanism. On the shaft ||9 is slidably mounted or splined a pinion |2| which may be slid on the shaft ||9, either free of the pinion ||5 or meshed with it so as to be driven at the same speed as the pinion I6. The pinion |2| is nor.. mally held in mesh'with the pinion I5 but may be slid free of it by a shifting 'fork |22 on af sliding rod |23 which extends through the end wall |20' and'isv provided at 'its projecting end with aknob |24. Whenthe knob is grasped and pulled, the gear ||2| is outo'f mesh with the gear rotate through a denite period of rotation-and then to actuate a reversing switch to reverse the rotation of the driving motor.

For this purpose the gear |2| meshes in all positions on the shaft ||9 with a. long pinion |25 rotatably mounted on a shaft |26 extending inwardly from the wall ||8 and having a reducedv end extending into a recess of an independently rotatable shaft |21. There is also fixed on the shaft i9 a second pinion |28 which meshes with a pinion |29 on the shaft |21. It will, therefore, be apparent that when the shaft |21 is rotated it rotates the pinion |29 and the pinion |20 and also rotates the pinion |2| and the pinion |25. This pinion, or gear drive, however, is so proportioned that the pinion |25 rotates at a slightly different speed from the pinion |29. This may be conveniently done by giving one of the pinions |29 or |25 one less tooth than the other as, for example, by giving the pinion |29 twenty-nine teeth, and the pinion |25 thirty teeth.

The pinion |29 has a flange |30 at the end nearest the pinion |25 and similarly the pinion |25 has a flange |3| facing the flange |30 and slightly spaced therefrom. Each of these flanges is provided with a notch |32 and |33 respectively and at their peripheral edges. The -shaft |21 is connected with a crank |34 on the outside of the head 33 whereby it may be rotated. This rotation is indicated on a dial |35, Fig. 3, which is driven from the crank |34 and shaft |21 through a speed reducing mechanism.

When the knob |24 is pulled out,.therefore, to disconnect the pinion |2| from the driving pinion ||5, and the crank |34 rotated to rotate the shaft |21, the flanges |30 and |3| will be rotated at different speeds so that the notches |32 and |33 will gradually move relatively to each other out of alignment. When the knob |24 is released and the pinion |2| moved to mesh with the pinion on the drive shaft H3, and the motor 6| started to rotate the lead screw spindle and tap forwardly, the gears |25 and |29 are rotated in the reverse direction by the pinion ||5. This rotation continues until the notches |32 and |33 come into alignment.

Between the two flanges |30 and |3| there is mounted a sliding reverse switch member |36, Figs. 10, 14 and 15, having a pin |31 extending on one side to rest against the periphery ofthe flange |30 or to enter the notch |32, and a'pin |38 aligned with the pin |31 and extending on the opposite side to rest on the periphery of flange |3| or to enter the notch |33.

' Assuming that the notches |32 and |33 are Y initi-ally in alignment and the pins |31 and |38 are received therein and that the flanges are -rotated counterclockwise as viewed in Fig. 14,

it will be apparent that the switch member |36 will be pushed upwardly against the action of f spring |39 confined between the switch member |35 and the stop |40 encircling the stem |4| of the switch member.

As the rotation'of the flanges |30, |3| continues, the notches move further out of alignment and it is impossible for both pinsV |31, |38 to entertheir respective notches at the same time and one of them is, therefore, always held against the periphery of the flange and theswitch member |36 is held upwardly against the action of the spring |39.. After rotating the vgear |29 counter-clockwise the knob |24 will be released and the pinion |2| meshes with the drive pinion H5, the mechanism will be in position tor start.

The motor 6| is controlled from the spindle head by means of a starting switch button |42 connected through connecting wires |43 With a starting and reversing switch |44, Fig. 12. When the button |42 is pressed the switch |44 is moved to starting position and the motor 6| starts and continues to drive the shaft 65, the lead screw spindle 98 and the control drive shaft ||3. This in turn rotates the pinion |2| and with it the pinions |25 and |29 in the opposite direction from that rotated by the crank |34 or in clockwise position, viewed i" Fig. 14.

This rotation continues proportional to the rotation of the lead screw spindle 98 until the notches |32 and |33 move into alignment. When this occurs and they approach the respective pins |31 and |38, these pins drop into the notches and are carried forward by the rotation of the flanges and by the action of the spring |39 moving the switch member |36. This in turn acts through a lever |45, Fig. 12, to actuate a reversing rod |46. 'This reverses the switch |44 and with it the motor 6| and the spindle 98 to withdraw the tap.

It will be apparent, therefore, that the rotation of the spindle 98 may be controlled by the extent to which the shaft |21 is rotated by the crank arm |34. The number of rotations of the handle |34 is indicated by the dial |35.

A chart |41, Fig. 2, is provided at the side of the head 33 giving the number of turns of the dial correspondingto different pitches of thread and the depth of the tap. For example, for a one inch depth the range on the dial for pitches of 26 to 11 will be from 39 to 1'?. Also, for example, the range for a 26 pitch from one-half to 'two inches will be from 20 to 78. Intermediate depths may be interpolated between these limits.

It is necessary, however, that once the reversing switch has been started, that it shall stop when the counting mechanism has returned to its initial starting position. This may be accomplished by a gear mechanism similar to the gears or pinions |2|, |25, |26, |29. For this purpose there is rigidly mounted on the shaft |1 a second gear |48, and correspondingly there is rotatably mounted on the shaft |26 a pinion |49 meshing with the pinion H6, and a pinion |50 meshing with the pinion |48. The teeth arrangement of these pinions is similar to that of the gear mechanism |2|, |29, but reversely positioned, for example, the pinion |50 has 29 teeth and the pinion |49 has 30 teeth, where the pinion |25 has 30 teeth, and the pinion |29, 29 teeth.

The pinions |49 and |50 also are provided with oppositely facing flanges |5| and |52 provided respectively with notches |53 and |54. Contrary to the position of the notches |32 and |33, the notches |53 and |54 are in alignment at the starting position and are rotated during the rotation of the shaft ||3 out of alignment so that when the notches |32 and |33 of flanges |30 and |3| come into alignment, the notches |53 and |54 have moved out of alignment a distance corresponding to that set on the dial |35.

A switch member |55 having projecting pins |56 and |51 is, therefore. held upwardly by the displaced position of the notches |53 and |54 being held -by the peripheral edges of the flanges |5|, |52, until the reverse rotation of the motor 6| brings the notches to aligned starting position, whereupon the switch member |55 will move downwardly to open the switch |44 and stop the rotation of the motor. The motor stops dead -when its circuit isl broken and, therefore, is

2,24 ,ses A A reversingswachbunon mis provided m the head whereby the motor 8| maybe reversed in'an emergency before'it reaches the limit set by the dial H35 and crank |34., It will be understood that the above mechanism is shown merely by way of example-and to give a preferred example of a counting and control v mech.

' Through the above invention we have provided a mechanism whereby` a tap may be held accurately in true position for inserting into a bore to be tapped, whereby the tap may be driven and beam vslidably 1n xed horizontglwjpsltion relative to said carriage, a motor on said ononem'v side of said carriage, a driving head on said beam on the opposite side of said carriage and in lead into the bore at the pitch set by the tap and without imposing any force or reaction on the free end of the tap or spindle, permitting its ,end to iioatso that the tap follows freely into the threads formed by it and these threads are,

therefore, formed without distortion and accuor to break the machinery even if the tap should not be accurately lset on a bore opening, or should not be set on any opening at all, because pressure thus exerted would be relieved by yielding of me spring los.

By means of the countercontrol and reversing "switch, it is only necessary to set the apparatus for any desired depth, as shown by the chart of Fis. 2, and push the starting button and the mechanism will thereupon advance the tap into the bore or opening accurately to the predetermined depth and then withdraw it.

What we claim is: 4

l. Apparatus for tapping which comprises a driving headto rotate and advance a tap holding spindle, a tap holding spindle rotatably mounted in said head and rotatable on its axis relative to said head and means to support said head to move freely in a plane transversely of said spindle during the rotation of said spindle.

2. Apparatus for tapping which comprises a driving head to rotate a tap holding spindle, a tap holding spindle rotatably mounted in said head and rotatable on its axis relative to said head, means to advance said spindle at the same rate of pitch of the tap to be held by said spindle and means to support said head to move freely in a plane transverse to the axis of said spindle during the rotation of said spindle.

3. Apparatus for tapping which comprises va carriage rotatable on a vertical axis, pairs of rollers in said carriage on opposite sides of the pivotal axis oi said carriage, a beam having surfaces engaged between the rollers of said pairs to hold said beam slidably in a iixed horizontal position relative to said carriage, a driving head on said beam to rotate and advance a tap holding spindle, a tap holding spindle extending downwardly from said head, a motor on said beam .on the opposite side of said rollers from said head and transmission mechanism from Asaid motor to said head.

4. Apparatus for tapping which comprises a carriage rotatable on a vertical axis and having pairs of rollers mounted o'n opposite sides ofthe axis of rotation of said carriage, a beam having nir'iaces engaged between said rollersfto hold said counterbalancing relation to said motor, a tap rotating and advancing means in said head and means driven by said motor to rotate said tap holding and rotating means.

5, Apparatus for tapping 'which compris a carriage rotatable on 'a vertical axis,'a. beam mounted on said cai'riage and having a pair of horizontal ilanges the ,upper edge of said lilanges being bevelled, pairs of rollers in said carriage engaging saidflanges on opposite sides of the axis ofrotation or said carriage to hold said beam in xed horizontal position and permit it to slide between said rollers, a driving head on a pro- Jecting end of said beam, a motor on said beamv `on the opposite side of 'said carriage. a tap rotating and advancing means in said head and means for driving-said rotating and advancing means from said motor.

6. Apparatus for tappingwhich comprises a carriage rotatable on a vertical axis, a beam mounted on said carriage and having a pair of horizontal flanges the upper edges of said flanges being beveled, pairs of rollers in said carriage e`ngaging said flanges on. opposite sides of the axis of rotation of said'carriage to hold said beam in xed horizontal position and permit it to slide between said rollers, a driving head on a projecting end of said beam, a motor on said beam on the opposite side of said carriage, a tap rotating and advancing means in said head and means for driving said rotating and advancing means from said motor, said driving means comprising a shaft extending longitudinally of said beam and carried thereby and transmission means Abetween said motor and said shaft and between said shaft and being bevelled, pairs of rollers in said carriage engaging said anges on opposite sides of the axis of rotation of said carriage to hold said beam in xed horizontal 4position and permit it to slide between said rollers, a driving head ona projecting end of ,said beam, a motor on said beam on the opposite side of said carriage, a Atap rotating and advancing means in said head and means for rotating said tapping and advancing means from said motor, means for counting the rotations of said tap rotating means and means for reversing said motor after said counting means has reached a predetermined count.

8. Apparatus for tapping which comprises means for rotatingand advancing a tap holding spindle, a counting mechanism driven by said rotating and advancing mechanism and comprising a pair of rotating elements differentially rotated towards alignmentby said driving mech- A anism and manually rotatable in the opposite direction to a distance to `correspond to the rotation and advance to be given to said spindle and means actuated by said counting means when said rotating elements are in alignment to stop said spindle rotating and advancing means. i

.9. Tapping mechanism which comprises means for rotating and advancing a-spindle and for. l

reversing saidrotation and withdrawing said spindle, counting means comprising rotating mechanism positively geared to, and driven by,

`holding and advancing spindle, means said spindle driving means toward a stopping position, manually operable means to move said counting means in the opposite direction fromv and said spindle, a countingmeans geared to and rotating to a stopping position in iixed relation to said spindle to move said switch mechanism to reversing position and manually operable means to rotate said counting means independently of said spindle to a position to predetermine the rotation and advance of said spindle to stopping position.

11. Tapping mechanism which comprises a tap holding and advancing spindle, a reversible motor having a starting and reversing switch mechanism, a transmission between said motor and said spindle to drive said spindle from said motor, a counting means geared to and rotating in fixed relation to said spindle, means operated by said lcounting means upon reaching a predetermined position to open said switch mechanism.

12. Tapping mechanism which comprisesa tap holding and advancing spindle, a 4reversible motor having a starting and reversing switch mechanism, a transmission mechanism between said motor and said spindle, a counting mechanism positively driven from said transmission to control mechanisms, the gears of each pair rotating at diierent speeds to rotate saidiirst pair of switch control elements into alignment4 and forward driving of said spindle, and `to rotate the second of said switch control elements into alignment upon the reverse movement of said spindle and driving mechanism.

16. Tapping mechanism of claim 15 having means for disengaging one set of gears from the common driving means and rotating it manually toa selected position.

17. Tapping mechanism of claim 15 in which said rotatable switch control elements each comprises a pair of discs driven from their respective gears and having a pair of peripheral notches and a switch actuating plunger having pins to be received in said notches when saidnotches are rotated into alignment.

18. Tapping mechanism which comprises `a. supporting carriage rotatable about a vertical axis and having supporting vrollers on opposite sides of said axis, a beam mounted between said rollers to slide in a horizontal direction on said carriage, a motor mounted on said beam on o'ne side of' said carriage, a reversing and stopping switch mechanism for said motor, a tapping head mounted on said beam on the opposite side of said carriage, a horizontal Vshaft extending lengthwise of said beam to drive said tapping head from said motor, a tap carrying spindle mounted vertically in said tapping head, gearing to drive said tap carrying spindle from said horlzontal shaft, a control mechanism geared to said horizontal shaft and comprising two pairs of such actuating elements, the elements of one pair when brought into alignment reversing said drive a pair of rotating mechanisms at different speeds and means operated by said rotating mechanismswhen'rotated into alignment to open said switch mechanism.

13. Tapping mechanism which comprises a tap for positively driving said spindle, counting mechanism comprising a pair of elements rotatable into aligned position to stop said spindle driving mechanism and a gearing driven from said spindle driving mechanism to rotate said elements at different speeds from a predetermined starting position to a position of alignment.

14. rI'apping mechanism of claim 13, in which said rotatable elements may be manually rotated to a selected starting position.

l5. Tapping mechanism which comprises a tap holding and advancing spindle, a reversible motor having a starting and reversing switch mechanism, a transmission between said motor and said spindle, a counting means positively driven in fixed relation to said spindle and driving means, a spindle control mechanism comprising two pairs of such control elements, one pair of which when brought into alignment reverses said -switch mechanism and the other pair of which when brought into alignment opens said switch mechanism to stop said motor, and two pairs oir gears, one pair for each of said switch switch mechanism of said motor, and the elements of the second pair opening said switch mechanism to stop said motor, and means in said control mechanism to drive said first pair toward alignment upon the forward driving of said spindle and to drive the elements of said second pair into alignment upon reverse rotation of said spindle.

19. Tapping mechanism which comprises means for rotating and advancing a spindle, counting means comprising rotating mechanism geared to and positively driven in fixed relation to the rotation of said spindle from a starting position to a stopping position and means controlled by said counting means to limit the rotation of said spindle between said starting and stopping positions.

20. Tapping mechanism which comprises means for rotating and advancing a spindle, counting means comprising rotating mechanism geared to and positively driven in fixed relation to the. rotation of said spindle from a starting position to a stopping position, means controlled by said counting means to limit the rotation of said spindle between,V said starting and stopping positions and manual means to rotate said counting mechanism relative to said spindle to adjust the distance between said starting and stopping positions.

JAMES A. EDEN. HARRY PHILLIPS. 

